The
services file is a local source of information
regarding each service available through the Internet. The
services file can be used in conjunction with or
instead of other services sources, including the NIS
maps "services.byname" and the NIS+ table
"services." Programs use the
getservbyname(3SOCKET) routines to access this
information.

The
services file contains an entry for each service.
Each entry has the form:

service-name port/protocol aliases
service-name

This is the official Internet
service name.

port/protocol

This field is composed of the
port number and protocol through which the service is
provided, for instance, 512/tcp.

aliases

This is a list of alternate
names by which the service might be requested.

Fields can be
separated by any number of SPACE and/or TAB
characters. A number sign (#) indicates the beginning
of a comment; any characters that follow the comment
character up to the end of the line are not interpreted by
routines which search the file.

Service names
may contain any printable character other than a field
delimiter, a NEWLINE, or a comment character.

Any changes to
a port assignment do not affect the actual port registration
of the service.